In general, in a case of coating vehicle bodies of automobiles, articles of furniture, electrical appliances, and the like with paint, a rotary atomizing head type coating machine that is excellent in a coating efficiency and coating finish of paint is used for coating. This rotary atomizing head type coating machine includes a tubular housing in an inner peripheral side of which a motor accommodating section is formed, an air motor that is accommodated in the motor accommodating section of the housing and drives and rotates a hollow rotational shaft, a rotary atomizing head that is positioned on the front side of the housing and is mounted to the front end of the rotational shaft in the air motor to spray paint supplied while rotating together with the rotational shaft, a feed tube that is provided inside the rotational shaft to axially extend with a radial gap to the rotational shaft to supply the paint to the rotary atomizing head, and a shaping air ring that is provided on the front side of the housing to eject shaping air for arranging a spraying pattern of the paint sprayed from the rotary atomizing head.
The air motor includes a motor case that is formed of a tubular body axially extending and is accommodated in the motor accommodating section, a rotational shaft that is provided in the motor case to axially extend therein, a turbine that is provided at a base end side of the rotational shaft and drives and rotates the rotational shaft by supply of turbine air thereto, a radial air bearing that is positioned on an outer peripheral side of the rotational shaft and is provided in the motor case to radially support the rotational shaft by supply of bearing air thereto, front and rear thrust air bearings that are provided in the motor case in such a manner as to interpose the turbine therebetween in the front-rear direction to support the rotational shaft in a thrust direction by supply of the bearing air thereto, a turbine air passage that includes an air supply passage for supplying the turbine air to the turbine and an air discharge passage for discharging exhaust air after driving and rotating the turbine, and a bearing air passage that supplies the bearing air to the radial air bearing and the front and rear thrust air bearings. With this configuration, the rotational shaft is supported in a non-contact state by the radial air bearing, and the turbine is supported in a non-contact state by the front thrust air bearing and the rear thrust air bearing.
An impeller with a plurality of rotor blades that radially extend to overlap in the circumferential direction is provided on the outer peripheral side of a general turbine. The turbine can rotate the rotational shaft at high speeds by spraying turbine air (compressed air) toward the impeller from an air nozzle (Patent Document 1).